Roofing Code: Section 1507

Requirements for Roof Coverings: Liquid-Applied Coatings

1507.15 Liquid-applied coatings. The installation of liquid-applied coatings shall comply with the provisions of this section.

1507.15.1 Slope. Liquid-applied roofs shall have a design slope of a minimum of one-fourth unit vertical in 12 units horizontal (2-percent slope).

Code Interpretation

This section implies that a minimum of ¼-inch per foot of slope is required for the application of liquid-applied roof coatings. This is easy to achieve in new construction where the slope can be designed into the deck. In remedial applications, achieving this slope may require artificial sloping methods with tapered insulation or saddles.

This code will become more prevalent now that more states and municipalities are adopting Energy Star-type codes for roof reflectance. These codes generally require roof reflectance rates to be above 65 percent the first three years - and most areas require reflectance rates above 70 percent. Achieving these rates is typically completed by applying liquid-applied roof coatings over the membrane surface. It is important to check with local codes authorities to determine if roof reflectance rates are imposed in your area.

WaterproofingCode: Section 1807

Dampproofing and Waterproofing: Ground-Water Control

1807.1.3 Ground-water control. Where the ground-water table is lowered and maintained at an elevation not less than 6 inches (152 mm) below the bottom of the lowest floor, the floor and walls shall be dampproofed in accordance with Section 1807.2. The design of the system to lower the ground-water table shall be based on accepted principles of engineering that shall consider, but not necessarily be limited to, permeability of the soil, rate at which water enters the drainage system, rated capacity of pumps, head against which pumps are to operate and the rated capacity of the disposal area of the system.

Interpretation of the Code

This section states that dampproofing is required if the water table is maintained a minimum of 6 inches below the bottom of the structure. If the water table is maintained within 6 inches of the bottom of the structure or if hydrostatic pressure exists, then waterproofing is required.

It is the designer’s responsibility to review site-engineering analysis for water table conditions and soil analysis to determine if and what type of dampproofing or waterproofing is required.